Replacement of Low Level Outlet valve for the Monroe Water Department Dam
Trinity Engineering & Technical Services was retained to design a replacement Low Level Outlet valve for the existing Monroe Water Department Dam. The dam provide fire flow and raw water to the municipal water supply system. The existing valve and operator were originally installed circa 1930 and have served the town well. The original Chapman Valve was a cast iron slide gate with brass surface seals and brass wedges to seat the valve against the thimble. The thimble was formed in the concrete dam when it was poured. The brass seals on the cast iron slide gate, had begun to fail resulting in leakage through the valve. At base flow conditions, typically during August, the leakage rates through the valve began to interfere with the ability of the municipality to maintain dam capacity to meet the potable and fire flow needs. The Low Level Outlet valve is positioned at the base of the dam to allow the dam to be completely drained for cleaning or maintenance and is essential to operating the dam and water supply.
Trinity specified a stainless steel slide gate manufactured by Whipps, Incorporated from Athol, MA.
Replacing the valve required close coordination between the municipal water system operators and fire departments since flow would be interrupted during the reinstallation of the valve. The old valve was removed and hoisted out of place using a temporary Davit Crane. The existing thimble also had to be removed from the upstream side of the dam. The new valve was installed using epoxy anchor bolts. After aligning the hand wheel operator, mid-shaft support and gate valve frame, the new stainless slide gate was grouted in place.
Stream flows were diverted to the potable and fire flow outlet pipes and discharged immediately downstream of the spillway using the existing diversion pipes. A submersible pump was used to maintain seepage behind the sand bag diversion.
The entire project was completed in 3 days and the new valve successfully leak checked.